Atomic and molecular hydrogen interacting with Pt(111)

This computational study is motivated by the apparent conflict between an e xperiment on dissociation of H-2 and D-2 on Pt(111), which suggests a rathe r corrugated potential energy surface (PES) for the H-2/Pt(111) system, and an experiment showing only weak nonzero-order diffraction of HD scattering from Pt(111). In the calculations we have used density functional theory ( DFT) within the generalized gradient approximation (GGA), including scalar relativistic effects and modelling the Pt(111) surface as a slab. We have f ound that the H-2/Pt(111) PES is both energetically and geometrically corru gated. We have also found that there are reaction paths without or with ver y low barriers leading to dissociation of H-2 on the Pt(111) surface, but t hat there are other reaction paths with substantial barriers. By performing extensive calculations on H interacting with a Pt(111) surface we have sho wn that a DFT/GGA approach that includes scalar relativistic effects is cap able of describing the interaction between a hydrogen atom and a Pt(111) su rface in a way that is, for the most part, consistent with experiments. (C) 1999 American Institute of Physics. [S0021-9606(99)70648-3].